Indo-European studies is a field of linguistics and an interdisciplinary field of study dealing with Indo-European languages, both current and extinct.^[1] Its goal is to amass information about the hypothetical proto-language from which all of these languages are descended, a language dubbed Proto-Indo-European (PIE), and its speakers, the Proto-Indo-Europeans, including their society and religion. The studies cover where the language originated and how it spread. This article also lists Indo-European scholars, centres, journals and book series.

Study methods[link]

Use of comparative linguistics[link]

The Comparative method was formally developed in the 19th century and applied first to Indo-European languages. The existence of the Proto-Indo-Europeans had been inferred by comparative linguistics as early as 1640, while attempts at an Indo-European proto-language reconstruction date back as far as 1713. However, by the 19th century, still no consensus was reached about the internal groups of the IE family.

Use of mass comparison[link]

Using the method of Mass comparison, the IE languages are sometimes considered to be part of super-families such as Nostratic or Eurasiatic.

Use of internal reconstruction[link]

The method of internal reconstruction is used to compare patterns within one dialect, without comparison with other dialects and languages, to try to arrive at an understanding of regularities operating at an earlier stage in that dialect. It has also been used to infer information about earlier stages of PIE than can be reached by the comparative method.

History of Indo-European studies[link]

Preliminary work[link]

By the time of Socrates (469-399 BC), the ancient Greeks were aware that their language had changed since the time of Homer (about 730 BC). Aristotle (about 330 BC) identified four types of linguistic change: insertion, deletion, transposition and substitution. In the 1st century BC, the Romans were aware of the similarities between Greek and Latin. There were also linguistic traditions in Mesopotamia and India; Pāṇini wrote a detailed grammar of Sanskrit in the 4th century BC.

In the post-classical West, languages studies were undermined by the naive attempt to derive all languages from Hebrew since the time of Saint Augustine. Prior studies classified the European languages as Japhetic. One of the first scholars to challenge the idea of a Hebrew root to the languages of Europe was Joseph Scaliger (1540–1609). He identified Greek, Germanic, Romance and Slavic languages groups by comparing the word for "God" in various European languages. In 1710, Leibniz applied ideas of gradualism and uniformitarianism to linguistics. Like Scaliger, he rejected a Hebrew root, but also rejected the idea of unrelated language groups and considered them all to have a common source.^{[citation needed]}

Around the 12th century, similarities between European languages became recognised. In Iceland, scholars noted the resemblances between Icelandic and English. Gerald of Wales claimed that Welsh, Cornish, and Breton were descendants of a common source. A study of the Insular Celtic languages was carried out by George Buchanan in the 16th century and the first field study was by Edward Lluyd around 1700. He published his work in 1707, shortly after publishing a translation of a study by Pezron on Breton.^{[citation needed]}

Dante (1265–1321) was aware of the fact that the Romance languages were related. Grammars of European languages other than Latin and Classical Greek began to be published at the end of the 15th century. This led to comparison between the various languages.^{[citation needed]}

In the 16th century, visitors to India became aware of similarities between Indian and European languages. For example, Filippo Sassetti reported striking resemblances between Sanskrit and Italian.^{[citation needed]}

Early Indo-European studies[link]

In a publication of 1647, Marcus Zuerius van Boxhorn proposed the existence of a primitive common language he called "Scythian". He included in its descendants Dutch, Greek, Latin, Persian and German, and in a posthumous publication of 1654 added Slavic, Celtic and Baltic. The 1647 publication discusses, as a first, the methodological issues in assigning languages to genetic groups. For example, he observed that loanwords should be eliminated in comparative studies, and also correctly put great emphasis on common morphological systems and irregularity as indicators of relationship.^[2] A few years earlier, Johann Elichmann already used the expression ex eadem origine (from a common source) in a 1640 study relating European languages to Indo-Iranian.^[2]

The concept of actually reconstructing an Indo-European proto-language was suggested by William Wotton in 1713, while showing, among others, that Icelandic ("Teutonic'), the Romance languages, and Greek were related.^[2]

Mikhail Lomonosov compared numbers and other linguistic features in different languages of the world including Slavic, Baltic ("Kurlandic"), Iranian ("Medic"), Finnish, Chinese, "Hottentot", and others. He emphatically expressed the antiquity of the linguistic stages accessible to comparative method in the drafts for his Russian Grammar published in 1755:^[3]

Imagine the depth of time when these languages separated! ... Polish and Russian separated so long ago! Now think how long ago [this happened to] Kurlandic! Think when [this happened to] Latin, Greek, German, and Russian! Oh, great antiquity!

Despite the above, the discovery of the genetic relationship of the whole family of Indo-European languages is often attributed to Sir William Jones, a British judge in India who in a 1786 lecture (published 1788) observed that

"The Sanskrit language, whatever be its antiquity, is of a wonderful structure; more perfect than the Greek, more copious than the Latin, and more exquisitely refined than either, yet bearing to both of them a stronger affinity, both in the roots of verbs and the forms of grammar, than could possibly have been produced by accident; so strong indeed, that no philologer could examine them all three, without believing them to have sprung from some common source, which, perhaps, no longer exists."^[4]

In his 1786 The Sanscrit Language, Jones postulated a proto-language uniting six branches - Sanskrit (i.e. Indo-Aryan), Persian (i.e. Iranian), Greek, Latin, Germanic and Celtic. In many ways his work was less accurate than his predecessors', as he erroneously included Egyptian, Japanese and Chinese in the Indo-European languages, while omitting Hindi.^[2]

In 1814 the young Dane Rasmus Christian Rask submitted an entry to an essay contest on Icelandic history, in which he concluded that the Germanic languages were (as we would put it) in the same language family as Greek, Latin, Slavic, and Lithuanian. He was in doubt about Old Irish, eventually concluding that it did not belong with the others (he later changed his mind), and further decided that Finnish and Hungarian were related but in a different family, and that "Greenlandic" (Kalaallisut) represented yet a third. He was unfamiliar with Sanskrit at the time. Later, however, he learned Sanskrit, and published some of the earliest Western work on ancient Iranian languages. August Schleicher was the first scholar to compose a tentative reconstructed text in the extinct common source Jones had predicted (see: Schleicher's fable). The reconstructed Proto-Indo-European language (PIE) represents, by definition, the common language of the Proto-Indo-Europeans. This early phase culminates in Franz Bopp's Comparative Grammar of 1833.

Later Indo-European studies[link]

The classical phase of Indo-European comparative linguistics leads from Bopp to August Schleicher's 1861 Compendium and up to Karl Brugmann's Grundriss published from the 1880s. Brugmann's junggrammatische re-evaluation of the field and Ferdinand de Saussure's proposal of the concept of "consonantal schwa" (which later evolved into the laryngeal theory) may be considered the beginning of "contemporary" Indo-European studies. The Indo-European proto-language as described in the early 1900s in its main aspects is still accepted today, and the work done in the 20th century has been cleaning up and systematization, as well as the incorporation of new language material, notably the Anatolian and Tocharian branches unknown in the 19th century, into the Indo-European framework.

Notably, the laryngeal theory, in its early forms barely noticed except as a clever analysis, became mainstream after the 1927 discovery by Jerzy Kuryłowicz of the survival of at least some of these hypothetical phonemes in Anatolian. Julius Pokorny in 1959 published his Indogermanisches etymologisches Wörterbuch, an updated and slimmed-down reworking of the three-volume Vergleichendes Wörterbuch der indogermanischen Sprachen of Alois Walde and Julius Pokorny (1927–32). Both of these works aim to provide an overview of the lexical knowledge accumulated until the early 20th century, but with only stray comments on the structure of individual forms; in Pokorny 1959, then-recent trends of morphology and phonology (e.g., the laryngeal theory), go unacknowledged, and he largely ignores Anatolian and Tocharian data.

The generation of Indo-Europeanists active in the last third of the 20th century, such as Oswald Szemerényi, Calvert Watkins, Warren Cowgill, Jochem Schindler, Helmut Rix, developed a better understanding of morphology and, in the wake of Kuryłowicz's 1956 Apophonie, ablaut. The Lexicon of the Indo-European verbs edited by Rix appeared in 1997 as a first step towards a modernization of Pokorny's dictionary; a corresponding tome addressing the noun is in preparation [1]. Current efforts are focused on a better understanding of the relative chronology within the proto-language, aiming at distinctions of "early", "middle" and "late", or "inner" and "outer" PIE dialects, but a general consensus has yet to form. From the 1960s, knowledge of Anatolian began to be of a certainty sufficient to allow it influence the image of the proto-language, see also Indo-Hittite.

Such attempts at recovering a sense of historical depth in PIE have been coupled with efforts towards coupling the history of the language with archaeology, notably with the Kurgan hypothesis. J. P. Mallory's 1989 In Search of the Indo-Europeans and 1997 Encyclopedia of Indo-European Culture gives an overview of this. Purely linguistic research was assisted by attempts to reconstruct the culture and religion of the Proto-Indo-Europeans by scholars such as Georges Dumézil, as well as by archaeology (e. g. Marija Gimbutas, Colin Renfrew) and genetics (e. g. Luigi Luca Cavalli-Sforza). These speculations about the realia of Proto-Indo-European culture are however not part of the field of comparative linguistics, but rather a sister-discipline.

Some concepts of Indo-European studies also influenced the Nazis. (See Aryan Race). In the period after World War II, several Indo-European scholars (e.g. Roger Pearson, Jean Haudry and the influential Georges Dumézil^[5]) and writers influenced by Indo-European studies (e.g. Alain de Benoist) were accused of having sympathies for Fascism or Nazism, and it was alleged that their political beliefs may have influenced their studies.^[6] Arvidsson speculated that the fact that many Indo-European scholars identify themselves as the descendants of the ancient Indo-Europeans may explain why the field of Indo-European studies has also been ideologically abused.^[7] Anthony remarked that "Indo-European linguistics and archaeology have been exploited to support openly ideological agendas for so long that a brief history of the issue quickly becomes entangled with the intellectual history of Europe."^[8]

In the 20th century, great progress was made due to the discovery of more language material belonging to the Indo-European family, and by advances in comparative linguistics, by scholars such as Ferdinand de Saussure.

List of Indo-European scholars[link]

(historical; see below for contemporary IE studies)

Journals[link]

• Kuhn's Zeitschrift KZ since 1852, in 1988 renamed to Historische Sprachforschung HS
• Indogermanische Forschungen IF since 1892
• Glotta since 1909
• Bulletin de la Société de Linguistique de Paris BSL
• Die Sprache since 1949
• Münchner Studien zur Sprachwissenschaft MSS 1952–
• Journal of Indo-European studies JIES since 1973
• Tocharian and Indo-European Studies since 1987
• Studia indo-europaea since 2001
• International Journal of Diachronic Linguistics and Linguistic Reconstruction IJDL Munich since 2004

Book series[link]

• Leiden Studies in Indo-European founded 1991
• Copenhagen Studies in Indo-European founded 1999
• Leiden Indo-European Etymological Dictionary Series founded 2005

Contemporary IE study centres[link]

The following universities have institutes or faculties devoted to IE studies:

This list is incomplete; you can help by expanding it.

Austria	Innsbruck [2] · Salzburg [3] · Vienna [4]
Czech Republic	Charles University in Prague [5]
Denmark	Copenhagen [6], [7], [8]
Germany	Bonn [9] · Cologne [10] · Dresden [11] · Erlangen [12] · Frankfurt am Main [13] · Free University of Berlin [14] · Freiburg [15] · Göttingen [16] · Hamburg [17]  · Halle [18] · Heidelberg [19][dead link] · Humboldt University of Berlin [20] · Jena [21] · Marburg [22] · Munich [23] · Münster [24] · Regensburg [25] · Würzburg [26]
Italy	Universita degli Studi di Padova
Netherlands	Leiden [27] [28]
Poland	Jagiellonian University [29]
Slovenia	Ljubljana [30]
Spain	Madrid [31] · Salamanca [32]
Sweden	Uppsala [33]
Switzerland	Basel [34] · Bern [35] · Lausanne [36] · Neuchâtel [37] · Zürich [38]
United Kingdom	Oxford [39]
United States	Cornell [40] · Harvard [41] · Los Angeles [42] · Texas [43]

Origin of the term[link]

The term Indo-European itself now current in English literature, was coined in 1813 by the British scholar Sir Thomas Young, although at that time, there was no consensus as to the naming of the recently discovered language family. However, he seems to have used it as a geographical term. Among the other names suggested were:

• indo-germanique (C. Malte-Brun, 1810)
• Indoeuropean (Th. Young, 1813)
• japetisk (Rasmus C. Rask, 1815)
• indisch-teutsch (F. Schmitthenner, 1826)
• sanskritisch (Wilhelm von Humboldt, 1827)
• indokeltisch (A. F. Pott, 1840)
• arioeuropeo (G. I. Ascoli, 1854)
• Aryan (F. M. Müller, 1861)
• aryaque (H. Chavée, 1867).

In English, Indo-German was used by J. C. Prichard in 1826 although he preferred Indo-European. In French, use of indo-européen was established by A. Pictet (1836). In German literature, Indoeuropäisch was used by Franz Bopp since 1835, while the term Indogermanisch had already been introduced by Julius von Klapproth in 1823, intending to include the northernmost and the southernmost of the family's branches, as it were as an abbreviation of the full listing of involved languages that had been common in earlier literature. Indo-Germanisch became established by the works of August Friedrich Pott, who understood it to include the easternmost and the westernmost branches, opening the doors to ensuing fruitless discussions whether it should not be Indo-Celtic, or even Tocharo-Celtic.

Today, Indo-European, Indo-Européen is well established in English and French literature, while Indogermanisch remains current in German literature, but alongside a growing number of uses of Indoeuropäisch.

Indo-Hittite is sometimes used for the wider family including Anatolian by those who consider that IE and Anatolian are comparable separate branches.

See also[link]

• Comparative method
• Historical linguistics
• Japhetic
• Proto-language

References[link]

External links[link]

• TITUS gallery of Indo-Europeanists
• Collection of articles dealing with the Indo-European studies

Indo-European
Geographic distribution:	Before the 16th century, Europe, and South, Central and Southwest Asia; today worldwide.
Linguistic classification:	One of the world's major language families
Proto-language:	Proto-Indo-European
Subdivisions:	Albanian Anatolian (extinct) Armenian Balto-Slavic (Baltic and Slavic) Celtic Germanic Hellenic (Greek) Indo-Iranian Italic (includes Romance) Tocharian (extinct)
ISO 639-2 and 639-5:	ine
Countries with a majority of speakers of IE languages   Countries with an IE minority language with official status

The Indo-European languages are a family (or phylum) of several hundred related languages and dialects,^[1] including most major current languages of Europe, the Iranian plateau, and South Asia and also historically predominant in Anatolia. With written attestations appearing since the Bronze Age, in the form of the Anatolian languages and Mycenaean Greek, the Indo-European family is significant to the field of historical linguistics as possessing the longest recorded history after the Afroasiatic family.

Indo-European languages are spoken by almost three billion native speakers,^[2] the largest number for any recognised language family. Of the twenty languages with the largest numbers of native speakers according to SIL Ethnologue, twelve are Indo-European: Spanish, English, Hindi, Portuguese, Bengali, Russian, German, Marathi, French, Italian, Punjabi, and Urdu, accounting for over 1.7 billion native speakers.^[3] Several disputed proposals link Indo-European to other major language families.

History of Indo-European linguistics[link]

Suggestions of similarities between Indian and European languages began to be made by European visitors to India in the 16th century. In 1583 Thomas Stephens, an English Jesuit missionary in Goa, noted similarities between Indian languages, specifically Konkani, and Greek and Latin. These observations, however, were included in a letter to his brother which was not published until the twentieth century.^[4]

The first account by a western European to mention the ancient language Sanskrit came from Filippo Sassetti (born in Florence, Italy in 1540), a merchant who traveled to the Indian subcontinent. Writing in 1585, he noted some word similarities between Sanskrit and Italian (these included devaḥ/dio "God", sarpaḥ/serpe "serpent", sapta/sette "seven", aṣṭa/otto "eight", nava/nove "nine").^[4] However, neither Stephens's nor Sassetti's observations led to further scholarly inquiry.^[4]

In 1647, Dutch linguist and scholar Marcus Zuerius van Boxhorn noted the similarity among Indo-European languages, and supposed that they derived from a primitive common language which he called "Scythian". He included in his hypothesis Dutch, Albanian, Greek, Latin, Persian, and German, later adding Slavic, Celtic and Baltic languages. However, Van Boxhorn's suggestions did not become widely known and did not stimulate further research.

Franz Bopp, pioneer in the field of comparative linguistic studies.

Gaston Coeurdoux and others had made observations of the same type. Coeurdoux made a thorough comparison of Sanskrit, Latin and Greek conjugations in the late 1760s to suggest a relationship between them. Similarly, Mikhail Lomonosov compared different languages groups of the world including Slavic, Baltic ("Kurlandic"), Iranian ("Medic"), Finnish, Chinese, "Hottentot", and others. He emphatically expressed the antiquity of the linguistic stages accessible to comparative method in the drafts for his Russian Grammar (published 1755).^[5]

The hypothesis reappeared in 1786 when Sir William Jones first lectured on the striking similarities between three of the oldest languages known in his time: Latin, Greek, and Sanskrit, to which he tentatively added Gothic, Celtic, and Old Persian,^[6] though his classification contained some inaccuracies and omissions.^{[7][dead link]}

It was Thomas Young who in 1813^[8] first used the term Indo-European, which became the standard scientific term through the work of Franz Bopp, whose systematic comparison of these and other old languages supported the theory. In some nations, the term Indo-Germanic is in use; in Germany as the standard scientific term, while in other languages it is the more common term.^[9] Bopp's Comparative Grammar, appearing between 1833 and 1852, counts as the starting point of Indo-European studies as an academic discipline.

The classical phase of Indo-European comparative linguistics leads from Franz Bopp's Comparative Grammar (1833) to August Schleicher's 1861 Compendium and up to Karl Brugmann's Grundriss, published in the 1880s. Brugmann's junggrammatische reevaluation of the field and Ferdinand de Saussure's development of the laryngeal theory may be considered the beginning of "modern" Indo-European studies. The generation of Indo-Europeanists active in the last third of the 20th century (such as Calvert Watkins, Jochem Schindler and Helmut Rix) developed a better understanding of morphology and, in the wake of Kuryłowicz's 1956 Apophonie, understanding of the ablaut.

Classification[link]

Indo-European language family

The approximate present-day distribution of the Indo-European branches within their homelands of Europe and Asia:

  Hellenic (Greek)

  Indo-Iranian

  Italic (includes Romance)

  Celtic

  Germanic

  Armenian

  Balto-Slavic (Baltic)

  Balto-Slavic (Slavic)

  Albanian

  Non-Indo-European languages

Dotted/striped areas indicate where multilingualism is common.

The various subgroups of the Indo-European language family include ten major branches, given in the chronological order of their earliest surviving written attestations:

1. Anatolian, the earliest attested branch. Isolated terms in Old Assyrian sources from the 19th century BC, Hittite texts from about the 16th century BC; extinct by Late Antiquity.
2. Hellenic, fragmentary records in Mycenaean Greek from between 1350 and 1450 BC have been found.^[10] Homeric texts date to the 8th century BC. (See Proto-Greek, History of the Greek.)
3. Indo-Iranian, descended from Proto-Indo-Iranian (dated to the late 3rd millennium BC).
   • Iranian, attested from roughly 1000 BC in the form of Avestan. Epigraphically from 520 BC in the form of Old Persian (Behistun inscription).
   • Indo-Aryan or Indic languages, attested from the late 15th to the early 14th century BC in Mitanni texts showing traces of Indo-Aryan. Epigraphically from the 3rd century BC in the form of Prakrit (Edicts of Ashoka). The Rigveda is assumed to preserve intact records via oral tradition dating from about the mid-2nd millennium BC in the form of Vedic Sanskrit.
   • Dardic
   • Nuristani
4. Italic, including Latin and its descendants (the Romance), attested from the 7th century BC.
5. Celtic, descended from Proto-Celtic. Tartessian dated from 8th century BC,^[11][12] Gaulish inscriptions date as early as the 6th century BC; Celtiberian from the 2nd century BC; Old Irish manuscript tradition from about the 8th century AD, and there are inscriptions in Old Welsh from the same period.
6. Germanic (from Proto-Germanic), earliest testimonies in runic inscriptions from around the 2nd century AD, earliest coherent texts in Gothic, 4th century AD. Old English manuscript tradition from about the 8th century AD.
7. Armenian, alphabet writings known from the beginning of the 5th century AD.
8. Tocharian, extant in two dialects (Turfanian and Kuchean), attested from roughly the 6th to the 9th century AD. Marginalized by the Old Turkic Uyghur Khaganate and probably extinct by the 10th century.
9. Balto-Slavic, believed by most Indo-Europeanists^[13] to form a phylogenetic unit, while a minority ascribes similarities to prolonged language contact.
   • Slavic (from Proto-Slavic), attested from the 9th century AD (possibly earlier; see Slavic runes), earliest texts in Old Church Slavonic.
   • Baltic, attested from the 14th century AD; for languages attested that late, they retain unusually many archaic features attributed to Proto-Indo-European (PIE).
10. Albanian, attested from the 14th century AD; Proto-Albanian likely emerged from Paleo-Balkan predecessors.^[14][15]

In addition to the classical ten branches listed above, several extinct and little-known languages have existed:

• Illyrian — related to Messapian.
• Venetic — close to Italic and possibly Continental Celtic.
• Liburnian — apparently grouped with Venetic.
• Messapian — not conclusively deciphered.
• Phrygian — language of the ancient Phrygians, possibly close to Thracian, Greek^{[citation needed]}.
• Paionian — extinct language once spoken north of Macedon.
• Thracian — possibly including Dacian.
• Dacian — possibly very close to Thracian.
• Ancient Macedonian — proposed relationships to Greek, Illyrian, Thracian, and Phrygian.
• Ligurian language — possibly not Indo-European; possibly close to or part of Celtic.
• Lusitanian — possibly related to (or part of) Celtic, or Ligurian, or Italic.

Grouping[link]

Membership of these languages in the Indo-European language family is determined by genetic relationships, meaning that all members are presumed to be descendants of a common ancestor, Proto-Indo-European. Membership in the various branches, groups and subgroups or Indo-European is also genetic, but here the defining factors are shared innovations among various languages, suggesting a common ancestor that split off from other Indo-European groups. For example, what makes the Germanic languages a branch of Indo-European is that much of their structure and phonology can so be stated in rules that apply to all of them. Many of their common features are presumed to be innovations that took place in Proto-Germanic, the source of all the Germanic languages.

Tree versus wave model[link]

To the evolutionary history of a language family, a genetic "tree model" is considered appropriate especially if communities do not remain in effective contact as their languages diverge. Exempted from this concept are shared innovations acquired by borrowing (or other means of convergence), that cannot be considered genetic. In this case the so-called "wave model" applies, featuring borrowings and no clear underlying genetic tree. It has been asserted, for example, that many of the more striking features shared by Italic languages (Latin, Oscan, Umbrian, etc.) might well be areal features. More certainly, very similar-looking alterations in the systems of long vowels in the West Germanic languages greatly postdate any possible notion of a proto-language innovation (and cannot readily be regarded as "areal", either, since English and continental West Germanic were not a linguistic area). In a similar vein, there are many similar innovations in Germanic and Balto-Slavic that are far more likely to be areal features than traceable to a common proto-language, such as the uniform development of a high vowel (*u in the case of Germanic, *i/u in the case of Baltic and Slavic) before the PIE syllabic resonants *ṛ,* ḷ, *ṃ, *ṇ, unique to these two groups among IE languages, which is in agreement with the wave model. The Balkan sprachbund even features areal convergence among members of very different branches.

Using an extension to the Ringe-Warnow model of language evolution, early IE was confirmed to have featured limited contact between distinct lineages, while only the Germanic subfamily exhibited a less treelike behaviour as it acquired some characteristics from neighbours early in its evolution rather than from its direct ancestors. The internal diversification of especially West Germanic is cited to have been radically non-treelike.^[16]

Proposed subgroupings[link]

Specialists have postulated the existence of such subfamilies (subgroups) as Italo-Celtic, Graeco-Armenian, Graeco-Aryan, and Germanic with Balto-Slavic. The vogue for such subgroups waxes and wanes; Italo-Celtic for example used to be a standard subgroup of Indo-European, but it is now little honored, in part because much of the evidence on which it was based has turned out to have been misinterpreted.^[17]

Subgroupings of the Indo-European languages are commonly held to reflect genetic relationships and linguistic change. The generic differentiation of Proto-Indo-European into dialects and languages happened hand in hand with language contact and the spread of innovations over different territories.

Rather than being entirely genetic, the grouping of satem languages is commonly inferred as an innovative change that occurred just once, and subsequently spread over a large cohesive territory or PIE continuum that affected all but the peripheral areas.^[18] Kortlandt proposes the ancestors of Balts and Slavs took part in satemization and were then drawn into the western Indo-European sphere.^[19]

Shared features of Phrygian and Greek^[20] and of Thracian and Armenian^[21] group together with the Indo-Iranian family of Indo-European languages.^[22] Some fundamental shared features, like the aorist (a verb form denoting action without reference to duration or completion) having the perfect active particle -s fixed to the stem, link this group closer to Anatolian languages^[23] and Tocharian. Shared features with Balto-Slavic languages, on the other hand (especially present and preterit formations), might be due to later contacts.^[24]

The Indo-Hittite hypothesis proposes the Indo-European language family to consist of two main branches: one represented by the Anatolian languages and another branch encompassing all other Indo-European languages. Features that separate Anatolian from all other branches of Indo-European (such as the gender or the verb system) have been interpreted alternately as archaic debris or as innovations due to prolonged isolation. Points proffered in favour of the Indo-Hittite hypothesis are the (non-universal) Indo-European agricultural terminology in Anatolia^[25] and the preservation of laryngeals.^[26] However, in general this hypothesis is considered to attribute too much weight to the Anatolian evidence. According to another view the Anatolian subgroup left the Indo-European parent language comparatively late, approximately at the same time as Indo-Iranian and later than the Greek or Armenian divisions. A third view, especially prevalent in the so-called French school of Indo-European studies, holds that extant similarities in non-satem languages in general - including Anatolian - might be due to their peripheral location in the Indo-European language area and early separation, rather than indicating a special ancestral relationship.^[27] Hans J. Holm, based on lexical calculations, arrives at a picture roughly replicating the general scholarly opinion and refuting the Indo-Hittite hypothesis.^[28]

Satem and centum languages[link]

The division of the Indo-European languages into a Satem vs. a Centum group was devised by von Bradke in the late 19th century.

Suggested macrofamilies[link]

Some linguists propose that Indo-European languages form part of a hypothetical Nostratic macrofamily, and attempt to relate Indo-European to other language families, such as South Caucasian, Uralic (the Indo-Uralic proposal), Dravidian, and Afroasiatic. This theory, like the similar Eurasiatic theory of Joseph Greenberg, and the Proto-Pontic postulation of John Colarusso, remains highly controversial, however, and is not accepted by most linguists in the field. Objections to such groupings are not based on any theoretical claim about the likely historical existence or non-existence of such macrofamilies; it is entirely reasonable to suppose that they might have existed. The serious difficulty lies in identifying the details of actual relationships between language families; it is very hard to find concrete evidence that transcends chance resemblance, or is not equally likely explained as being due to borrowing (including Wanderwörter, which can travel very long distances). Since the signal-to-noise ratio in historical linguistics declines steadily over time, at great enough time-depths it becomes open to reasonable doubt that it can even be possible to distinguish between signal and noise.

Evolution[link]

Proto-Indo-European[link]

Scheme of Indo-European migrations from ca. 4000 to 1000 BC according to the Kurgan hypothesis.

The Proto-Indo-European language (PIE) is the common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans. From the 1960s, knowledge of Anatolian became certain enough to establish its relationship to PIE. Using the method of internal reconstruction an earlier stage, called Pre-Proto-Indo-European, has been proposed.

PIE was an inflected language, in which the grammatical relationships between words were signaled through inflectional morphemes (usually endings). The roots of PIE are basic morphemes carrying a lexical meaning. By addition of suffixes, they form stems, and by addition of desinences (usually endings), these form grammatically inflected words (nouns or verbs). The hypothetical Indo-European verb system is complex and, like the noun, exhibits a system of ablaut.

Diversification[link]

This unreferenced section requires citations to ensure verifiability.

The diversification of the parent language into the attested branches of daughter languages is historically unattested. The timeline of the evolution of the various daughter languages, on the other hand, is mostly undisputed, quite regardless of the question of Indo-European origins.

Indo-European languages ca. 1500 BC

Indo-European languages ca. 500 BC

Indo-European languages ca. 500 AD

• 2500 BC–2000 BC: The breakup into the proto-languages of the attested dialects is complete. Proto-Greek is spoken in the Balkans, Proto-Indo-Iranian north of the Caspian in the emerging Andronovo culture. The Bronze Age reaches Central Europe with the Beaker culture, likely composed of various Centum dialects. The Tarim mummies possibly correspond to proto-Tocharians.
• 2000 BC–1500 BC: Catacomb culture north of the Black Sea. The chariot is invented, leading to the split and rapid spread of Iranian and Indo-Aryan from the Bactria-Margiana Archaeological Complex over much of Central Asia, Northern India, Iran and Eastern Anatolia. Proto-Anatolian is split into Hittite and Luwian. The pre-Proto-Celtic Unetice culture has an active metal industry (Nebra skydisk).
• 1500 BC–1000 BC: The Nordic Bronze Age develops pre-Proto-Germanic, and the (pre)-Proto-Celtic Urnfield and Hallstatt cultures emerge in Central Europe, introducing the Iron Age. Migration of the Proto-Italic speakers into the Italian peninsula (Bagnolo stele). Redaction of the Rigveda and rise of the Vedic civilization in the Punjab. The Mycenaean civilization gives way to the Greek Dark Ages.
• 1000 BC–500 BC: The Celtic languages spread over Central and Western Europe. Baltic languages are spoken in a huge area from present-day Poland to the Ural Mountains.^[29] Proto Germanic. Homer and the beginning of Classical Antiquity. The Vedic Civilization gives way to the Mahajanapadas. Siddhartha Gautama preaches Buddhism. Zoroaster composes the Gathas, rise of the Achaemenid Empire, replacing the Elamites and Babylonia. Separation of Proto-Italic into Osco-Umbrian and Latin-Faliscan. Genesis of the Greek and Old Italic alphabets. A variety of Paleo-Balkan languages are spoken in Southern Europe.
• 500 BC–1 BC/AD: Classical Antiquity: spread of Greek and Latin throughout the Mediterranean, and during the Hellenistic period (Indo-Greeks) to Central Asia and the Hindukush. Kushan Empire, Mauryan Empire. Proto-Germanic. The Anatolian languages are extinct.
• 1 BC/AD 500: Late Antiquity, Gupta period; attestation of Armenian. Proto-Slavic. The Roman Empire and then the Migration period marginalize the Celtic languages to the British Isles.
• 500–1000: Early Middle Ages. The Viking Age forms an Old Norse koine spanning Scandinavia, the British Isles and Iceland. The Islamic conquest and the Turkic expansion results in the Arabization and Turkification of significant areas where Indo-European languages were spoken. Tocharian is extinct in the course of the Turkic expansion while Northeastern Iranian (Scytho-Sarmatian) is reduced to small refugia. Slavic languages spread over wide areas in eastern and southeastern Europe, largely replacing Romance in the Balkans (with the exception of Romanian) and whatever was left of the paleo-Balkan languages (with the exception of Albanian).
• 1000–1500: Late Middle Ages: Attestation of Albanian and Baltic.
• 1500–2000: Early Modern period to present: Colonialism results in the spread of Indo-European languages to every continent, most notably Romance (North, Central and South America, French Canada, North and Sub-Saharan Africa, West Asia), West Germanic (English in North America, Sub-Saharan Africa, East Asia and Australia; to a lesser extent Dutch and German), and Russian to Central Asia and North Asia.

Sound changes[link]

As the Proto-Indo-European (PIE) language broke up, its sound system diverged as well, changing according to various sound laws evidenced in the daughter languages.

PIE is normally reconstructed with a complex system of 15 stop consonants, including an unusual three-way phonation (voicing) distinction between voiceless, voiced and "voiced aspirated" (i.e. breathy voiced) stops, and a three-way distinction among velar consonants (k-type sounds) between "palatal" ḱ ǵ ǵh, "plain velar" k g gh and labiovelar kʷ gʷ gʷh. (The correctness of the terms palatal and plain velar is disputed; see Proto-Indo-European phonology.) All daughter languages have reduced the number of distinctions among these sounds, often in divergent ways.

As an example, in English, one of the Germanic languages, the following are some of the major changes that happened:

1. As in other centum languages, the "plain velar" and "palatal" stops merged, reducing the number of stops from 15 to 12.
2. As in the other Germanic languages, the Germanic sound shift changed the realization of all stop consonants, with each consonant shifting to a different one:

   bʰ → b → p → f

   dʰ → d → t → θ

   gʰ → g → k → h

   gʷʰ → gʷ → kʷ → hʷ

   Each original consonant shifted one position to the right. For example, original dʰ became d, while original d became t and original t became θ (written th in English). This is the original source of the English sounds written f, th, h and wh. Examples, comparing English with Latin, where the sounds largely remain unshifted:

   For PIE p: piscis vs. fish; pēs, pēdis vs. foot; pluvium "rain" vs. flow; pater vs. father

   For PIE t: trēs vs. three; māter vs. mother

   For PIE d: decem vs. ten; pēdis vs. foot; quid vs. what

   For PIE k: centum vs. hund(red); capere "to take" vs. have

   For PIE kʷ: quid vs. what; quandō vs. when

3. Various further changes affected consonants in the middle or end of a word:
   • The voiced stops resulting from the sound shift were softened to voiced fricatives (or perhaps the sound shift directly generated fricatives in these positions).
   • Verner's law also turned some of the voiceless fricatives resulting from the sound shift into voiced fricatives or stops. This is why the t in Latin centum ends up as d in hund(red) rather than the expected th.
   • Most remaining h sounds disappeared, while remaining f and th became voiced. For example, Latin decem ends up as ten with no h in the middle (but note taíhun "ten" in Gothic, an archaic Germanic language). Similarly, the words seven and have have a voiced v (compare Latin septem, capere), while father and mother have a voiced th, although not spelled differently (compare Latin pater, māter).

None of the daughter-language families (except possibly Anatolian, particularly Luvian) reflect the plain velar stops differently from the other two series, and there is even a certain amount of dispute whether this series existed at all in PIE. The major distinction between centum and satem languages corresponds to the outcome of the PIE plain velars:

• The "central" satem languages (Indo-Iranian, Balto-Slavic, Albanian and Armenian) reflect both "plain velar" and labiovelar stops as plain velars, often with secondary palatalization before a front vowel (e i ē ī). The "palatal" stops are palatalized and often appear as sibilants (usually but not always distinct from the secondarily palatalized stops).
• The "peripheral" centum languages (Germanic, Italic, Celtic, Greek, Anatolian and Tocharian) reflect both "palatal" and "plain velar" stops as plain velars, while the labiovelars continue unchanged, often with later reduction into plain labial or velar consonants.

The three-way PIE distinction between voiceless, voiced and voiced aspirated stops is considered extremely unusual from the perspective of linguistic typology — particularly in the existence of voiced aspirated stops without a corresponding series of voiceless aspirated stops. None of the various daughter-language families continue it unchanged, with numerous "solutions" to the apparently unstable PIE situation:

• The Indo-Aryan languages preserve the three series unchanged but have evolved a fourth series of voiceless aspirated consonants.
• The Iranian languages probably passed through the same stage, subsequently changing the aspirated stops into fricatives.
• Greek converted the voiced aspirates into voiceless aspirates.
• Italic probably passed through the same stage, but reflects the voiced aspirates as voiceless fricatives, especially f (or sometimes plain voiced stops in Latin).
• Celtic, Balto-Slavic, Anatolian and Albanian merge the voiced aspirated into plain voiced stops.
• Germanic and Armenian change all three series in a chain shift, with e.g. bh b p becoming b p f (known as Grimm's law in Germanic).

Among the other notable changes affecting consonants are:

• The Ruki sound law (s becomes /ʃ/ before r, u, k, i) in the satem languages.
• Loss of prevocalic p in Proto-Celtic.
• Development of prevocalic s to h in Proto-Greek, with later loss of h between vowels.
• Verner's law in Proto-Germanic.
• Grassmann's law (dissimilation of aspirates) independently in Proto-Greek and Proto-Indo-Iranian.

The following table shows the basic outcomes of PIE consonants in some of the most important daughter languages for the purposes of reconstruction. For a fuller table, see Indo-European sound laws.

Notes:

• C- At the beginning of a word.
• -C- Between vowels.
• -C At the end of a word.
• `-C- Following an unstressed vowel (Verner's law).
• -C-^(rl) Between vowels, or between a vowel and r, l (on either side).
• C^T Before a (PIE) stop (p, t, k).
• C^T- After a (PIE) obstruent (p, t, k, etc.; s).
• C^(T) Before or after an obstruent (p, t, k, etc.; s).
• C^H Before an original laryngeal.
• C^E Before a (PIE) front vowel (i, e).
• C^E' Before secondary (post-PIE) front-vowels.
• C^e Before e.
• C^(u) Before or after a (PIE) u.
• C^(O) Before or after a (PIE) o, u.
• C^n- After n.
• C^R Before a sonorant (r, l, m, n).
• C^(R) Before or after a sonorant (r, l, m, n).
• C^(r),l,u- Before r, l or after r, u.
• C^ruki- After r, u, k, i (Ruki sound law).
• C^..Ch Before an aspirated consonant in the next syllable (Grassmann's law, aka dissimilation of aspirates).
• C^E..Ch Before a (PIE) front vowel (i, e) as well as before an aspirated consonant in the next syllable (Grassmann's law, aka dissimilation of aspirates).
• C^(u)..Ch Before or after a (PIE) u as well as before an aspirated consonant in the next syllable (Grassmann's law, aka dissimilation of aspirates).

Comparison of conjugations[link]

The following table presents a comparison of conjugations of the thematic present indicative of the verbal root *bʰer- of the English verb to bear and its reflexes in various early attested IE languages and their modern descendants or relatives, showing that all languages had in the early stage an inflectional verb system.